poetee



D. D. PORTER. PROPBIILING STEAM VESSELS.

Patented Jane 12, 1860.

il/z'inesse @Lr Laerzi'ar: ZIWJ/ M 4 STATES PATENT OFFICE.

DAVID D. PORTER, OF THE UNITED STATES NAVY.

MARINE PROPELLER.

Specification of Letters Patent No. 28,688, dated June 12, 1860.

To all whom it may concern:

Be it known that I, DAVID D. PORTER, a lieutenant in the United States Navy, and at present stationed at the navy-yard, near Portsmouth, in the county of Rockingham and State of New Hampshire, have invented an Improvement Relating to the Propelling of Steam Vessels; and I do hereby declare that the same is fully described and represented in the following specification and the accompanying drawings, of which Figure 1, is a side view of a propeller constructed in accordance with my invention. Fig. 2, is an end view of it.

The nature of my improvement consists in a peculiar arrangement of blades and the wing fianches orrepressors of the centrifugal motion, such arrangement not only permitting the propeller to be triced up in the usual manner into the well at' the stern of a vessel, but being efiicacious in other respects.

The ordinary screw propellers of whatever kind, generally have their blades set at right angles with the shaft and with a suitable pitch and length of screw; each of which screws when unprovided with fianches on their blades have not been perfectly effective on account of what steam engineers term the slip.

It is a well established fact, that the loss as they would be obliged to do if working in a solid.

When a screw is set in motion in a screw ship, there are two forces acting upon the Water at the same time, they resulting from the oblique action of the revolving blades. One is a repulsive force and the other is a centrifugal force, which acting at right angles with each other, the water pressed upon is sent ofi in the diagonal of a parallelogram nearly, or more properly speaking, forms the frustum of a cone.

It is desirable in order to obtain the greatest power, and the least slip, that the water should recede from the propeller in the shape of a cylinder which can only be arrived at by lessening the centrifugal force,

and instead of having the water deflected outward, to have it delivered parallel to the axis of the shaft. While this object is best gained by providing the blades with the fianches or repressors, my plan or improvement in arranging them causes the propeller to act in a more perfect manner, than when the fianches or repressors are each disposed at an equal distance from the axis of the shaft.

Where only two blades of equal length are employed and are provided with fianches or repressors all the fianches act in one circular or tubular path. It has been found that by arranging the fianches so that they may be at different distances from the axis of the shaft, that an improvement in the action of the propeller results. reason in constructing a screw propeller, on my improved plan, I make it with four flanched blades, two of which are shorter than the other two, so that the fianches of two may be arranged so as to travel in a tubular path or paths separate from and within that or those of the other fianches. Each shorter blade with its fianch, while operating to propel the vessel, checks the radial velocity of the water so as to enable the next succeeding longer blade to act to better advantage on the water, than it otherwise would. Thus, important advantages ensue from my invention.

In the drawings, A, denotes the hub of the propeller; B, B, its longer blades; C, C, the shorter blades each being arranged between two longer blades; D, D, are the fianches (or repressors) of the longer blades, while E, E, are those of the shorter blades. The fianches E, E, while the propeller may be in revolution, will run in a path or paths having a diameter less than that of the path or paths of rotation of the fianches With my arrangement of the fianches and employment of the short wings in connection with longer ones as described, the effect of vibration at the stern of the vessel is diminished, there is less Waste of power and more regularity of action of the propeller.

I do not claim a propeller made with four blades; nor do I claim applying fianches to the blades, when such fianches are arranged so that each of them is placed at a like distance from the axis of the shaft For this whereby all are caused to travel in one tubular path. My invention is an improvement on such a propeller.

I claim My improved propeller as constructed with the new arrangement of Wings and flanches substantially as above described and as represented in the accompanying drawings.

DAVID D. PORTER.

WVitnesses:

A. A. HENDERSON, GEO. F. CUTTER. 

